Nowadays, thermoplastic polymers are frequently made flame-retardant by adding phosphorus- or halogen-containing compounds. Mixtures of phosphorus- and nitrogen-containing compounds are also used as flame-retardant agents. However, the flame-retardant effect is too weak or the thermal stability of the resulting flame-retardant plastic is too low.
Salts of phosphinic acids have also been shown to be effective flame-retardant additives for polymers, producing minor changes in the thermal properties of the plastic, but still showing an insufficient flame-retardant effect. Halogen-containing organic compounds are assumed to act by chemically or physically interfering with combustion processes. It is assumed that e.g. organic halogen forms (such as decabromodiphenyl oxide, hexabromocyclodecane and tetrabromobisphenol A) produce hydrogen bromide which interacts with the free radical organic polymer.
In the recent years however, individual brominated flame retardants (e.g. polybrominated diphenyl ethers) were found potentially harmful to the environment and human health. Based on the results of the assessment of the dangers of brominated flame retardants, the provisions of the European Union since July 2006 prohibited the production and use of pentabromodiphenyl ether and octabromodiphenyl oxide, while limiting decabromodiphenyl oxide to certain uses. Various derivatives, for example ether, ester and carbonate derivatives, of pentaerythritol phosphate are known as flame retardant additives. A bromine-containing pentaerythritol phosphoester, pentaerythritol double-spiro phosphoryl double-tribromo neopentyl alcohol ester, is also known as a fire retardant.
Various hindered amines are commercially available and known to achieve thermal stabilization of various classes of thermoplastic polymers, especially when the latter are in the form of thin films. Flame retardant polyolefin pre-expanded particles made from a resin composition comprising a polyolefin and a triazine-containing hindered amine ether flame retardant are also known in the art, especially from Patent Literature 1. Patent Literature 2 discloses that the addition of carbon black to polyolefins does not impart a pre-expanded and foamed article therefrom with enhanced flame resistance but worsens the burning behavior. Patent Literature 2 also discloses that the incorporation of powdered activated carbon (hereinafter referred to as “PAC”) and a triazine-containing hindered amine ether flame retardant in a foamed polyolefin further increases flame resistance.
Patent Literature 3 discloses that the incorporation of a phosphoric ester and a triazine-containing hindered amine ether flame retardant in an expanded polyolefin particle further increases flame resistance and does not generate harmful gases when burning.
Patent Literature 4 discloses that the incorporation of a triarylphosphine oxide and a triazine-containing hindered amine ether flame retardant in an expanded polyolefin particle with addition of at least 0.5% by weight carbon black, further increases flame resistance.
Patent Literature 5 discloses a thermoplastic polymer foamed article containing carbon black and a triazine-containing hindered amine ether.
Patent Literature 6 discloses a composition containing a hindered amine, phosphite, and the like.
Patent Literature 7 discloses a flame-retardant composition containing a sterically hindered alkoxyamine stabilizer, phosphazene, and the like.
Patent Literature 8 discloses a flame-retardant polymer composition containing a sterically hindered amine stabilizer, a phosphorous flame retardant, and the like.
Patent Literature 9 discloses a composition containing a hindered hydrocarbyloxy amine stabilizer.
Patent Literature 10 discloses a process for producing a flame-retardant polyolefin foam with use of a combination of a phosphorous compound and a 1,3,5-triazine compound as a flame retardant.
Patent Literature 11 discloses a mixture containing a phosphonate compound, a 1,3,5-triazine compound, and the like.